- `[2026-07-14]` **MTP-on-modelopt: NO checkpoint config skips the spec-decode drafter's quant (vLLM 0.24 bug) — 4 config attempts failed before the runtime workaround.** All crashed the same way (`qwen3_5_mtp.py:256` `param_data.shape == loaded_weight.shape` AssertionError — bf16 mtp head loaded into a quantized drafter param): (1) mtp excludes in `config.json` (WRONG file — vLLM modelopt reads `hf_quant_config.json`); (2) specific-unfused mtp names in hf_quant_config; (3) wildcards `mtp*`/`mtp.layers.0*` (`is_layer_skipped` is EXACT-membership, NOT glob — wildcards match nothing); (4) exact fused+unfused names in both `mtp.`/`model.` prefixes. Instrumenting `is_layer_skipped` proved the drafter's exclude list holds ONLY the main model's `linear_attn` entries — the mtp excludes never reach the draft-model quant config. ONLY fix = a mounted `sitecustomize` force-skipping `mtp.*`. LESSON: don't chase checkpoint-config fixes for the mtp-drafter crash; go straight to the runtime patch. Also `nvidia-modelopt[hf]==0.43` (AEON's producer version) is a trap — it pins transformers back to 4.57 which can't load `qwen3_5` at all; use 0.45 + the FusedMoE guard in `quant_modelopt.py`.